This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is powered by a 9 V battery, as its consumption is very low.
This tester from a 1960 magazine is only for capacitors with insulation voltages above 200 V (110...
Found in an English documentation from 1977, this circuit activates a relay according to the...
August 2017 - This Maxim component, available from Mouser Electronics, is ideal for wearables,...